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Statistics & SPSS Review Fall 2009

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Statistics & SPSS Review. Fall 2009. Types of Measures / Variables. Nominal / categorical Gender, major, blood type, eye color Ordinal Rank-order of favorite films; Likert scales? Interval / scale Time, money, age, GPA. Main Analysis Techniques. Main Analysis Techniques. - PowerPoint PPT Presentation

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Page 1: Statistics & SPSS Review

Statistics & SPSS Review

Fall 2009

Page 2: Statistics & SPSS Review

Types of Measures / Variables

• Nominal / categorical– Gender, major, blood type, eye color

• Ordinal– Rank-order of favorite films; Likert scales?

• Interval / scale– Time, money, age, GPA

Page 3: Statistics & SPSS Review

Variable Type Example Commonly-used Statistical

Method

Nominal by Nominal blood type by gender

Chi-square

Scale by Nominal GPA by gender

GPA by major

t-test

Analysis of Variance

Scale by Scale weight by heightGPA by SAT

RegressionCorrelation

Main Analysis Techniques

Page 4: Statistics & SPSS Review

Variable Type Example Commonly-used Statistical

Method

Nominal by Nominal blood type by gender

Chi-square

Scale by Nominal GPA by gender

GPA by major

t-test

Analysis of Variance

Scale by Scale weight by heightGPA by SAT

RegressionCorrelation

Main Analysis Techniques

Page 5: Statistics & SPSS Review

SPSS Cross –tab with Chi-Squarevictim gender * probation or jail Crosstabulation

3 21 2412.5% 87.5% 100.0%

9 15 2437.5% 62.5% 100.0%

12 36 4825.0% 75.0% 100.0%

Count% within victim genderCount% within victim genderCount% within victim gender

female

male

victim gender

Total

probation jailprobation or jail

Total

Chi-Square Tests

4.000b 1 .0462.778 1 .0964.144 1 .042

.093 .047

3.917 1 .048

48

Pearson Chi-SquareContinuity Correctiona

Likelihood RatioFisher's Exact TestLinear-by-LinearAssociationN of Valid Cases

Value dfAsymp. Sig.

(2-sided)Exact Sig.(2-sided)

Exact Sig.(1-sided)

Computed only for a 2x2 tablea.

0 cells (.0%) have expected count less than 5. The minimum expected count is 6.00.

b.

Page 6: Statistics & SPSS Review

SPSS Cross –tab with Chi-Squarevictim gender * probation or jail Crosstabulation

3 21 2412.5% 87.5% 100.0%

9 15 2437.5% 62.5% 100.0%

12 36 4825.0% 75.0% 100.0%

Count% within victim genderCount% within victim genderCount% within victim gender

female

male

victim gender

Total

probation jailprobation or jail

Total

Chi-Square Tests

4.000b 1 .0462.778 1 .0964.144 1 .042

.093 .047

3.917 1 .048

48

Pearson Chi-SquareContinuity Correctiona

Likelihood RatioFisher's Exact TestLinear-by-LinearAssociationN of Valid Cases

Value dfAsymp. Sig.

(2-sided)Exact Sig.(2-sided)

Exact Sig.(1-sided)

Computed only for a 2x2 tablea.

0 cells (.0%) have expected count less than 5. The minimum expected count is 6.00.

b.

p < .05

Page 7: Statistics & SPSS Review

Variable Type Example Commonly-used Statistical

Method

Nominal by Nominal blood type by gender

Chi-square

Scale by Nominal GPA by gender

GPA by major

t-test

Analysis of Variance

Scale by Scale weight by heightGPA by SAT

RegressionCorrelation

Main Analysis Techniques

Page 8: Statistics & SPSS Review

SPSS t-test Output

Group Statistics

24 16.04 12.723 2.59724 6.00 9.227 1.883

victim genderfemalemale

lengthofsentave11N Mean Std. Deviation

Std. ErrorMean

Independent Samples Test

.824 .369 3.130 46 .003 10.042 3.208 3.584 16.499

3.130 41.951 .003 10.042 3.208 3.567 16.516

Equal variancesassumedEqual variancesnot assumed

lengthofsentave11F Sig.

Levene's Test forEquality of Variances

t df Sig. (2-tailed)Mean

DifferenceStd. ErrorDifference Lower Upper

95% ConfidenceInterval of the

Difference

t-test for Equality of Means

Page 9: Statistics & SPSS Review

SPSS t-test Output

Group Statistics

24 16.04 12.723 2.59724 6.00 9.227 1.883

victim genderfemalemale

lengthofsentave11N Mean Std. Deviation

Std. ErrorMean

Independent Samples Test

.824 .369 3.130 46 .003 10.042 3.208 3.584 16.499

3.130 41.951 .003 10.042 3.208 3.567 16.516

Equal variancesassumedEqual variancesnot assumed

lengthofsentave11F Sig.

Levene's Test forEquality of Variances

t df Sig. (2-tailed)Mean

DifferenceStd. ErrorDifference Lower Upper

95% ConfidenceInterval of the

Difference

t-test for Equality of Means

1. Read means

2. Read Levene’s Test 3. Read p value

Page 10: Statistics & SPSS Review

Variable Type Example Commonly-used Statistical Method

Nominal by Nominal blood type by gender

Chi-square

Scale by Nominal GPA by gender

GPA by major

t-test

Analysis of Variance

Scale by Scale weight by heightGPA by SAT

RegressionCorrelation

Analysis of Variance

Page 11: Statistics & SPSS Review

SPSS ANOVA outputDescriptives

lengthofsentave11

19 14.26 15.183 3.483 6.94 21.58 0 6014 7.43 8.474 2.265 2.54 12.32 0 2415 10.27 10.067 2.599 4.69 15.84 0 3648 11.02 12.109 1.748 7.50 14.54 0 60

natural sciencesocial sciencearts and humanitiesTotal

N Mean Std. Deviation Std. Error Lower Bound Upper Bound

95% Confidence Interval forMean

Minimum Maximum

ANOVA

lengthofsentave11

388.933 2 194.467 1.346 .2716502.046 45 144.4906890.979 47

Between GroupsWithin GroupsTotal

Sum ofSquares df Mean Square F Sig.

Page 12: Statistics & SPSS Review

SPSS ANOVA outputDescriptives

lengthofsentave11

19 14.26 15.183 3.483 6.94 21.58 0 6014 7.43 8.474 2.265 2.54 12.32 0 2415 10.27 10.067 2.599 4.69 15.84 0 3648 11.02 12.109 1.748 7.50 14.54 0 60

natural sciencesocial sciencearts and humanitiesTotal

N Mean Std. Deviation Std. Error Lower Bound Upper Bound

95% Confidence Interval forMean

Minimum Maximum

ANOVA

lengthofsentave11

388.933 2 194.467 1.346 .2716502.046 45 144.4906890.979 47

Between GroupsWithin GroupsTotal

Sum ofSquares df Mean Square F Sig.

p value

Page 13: Statistics & SPSS Review

Variables & Statistical TestsVariable Type Example Common Stat

MethodNominal by nominal

Blood type by gender

Chi-square

Scale by nominal GPA by genderGPA by major

T-testAnalysis of Variance

Scale by scale Weight by heightGPA by SAT

RegressionCorrelation

Page 14: Statistics & SPSS Review

Variance

x i - Mean )2

Variance = s2 = ----------------------- N

 

Standard Deviation = s = variance

Page 15: Statistics & SPSS Review

Regression line

W = 3.3 H - 73

Page 16: Statistics & SPSS Review

Scatterplot: Sentence by G.P.A.

Page 17: Statistics & SPSS Review

Regression Coefficients

Coefficientsa

17.853 12.097 1.476 .155-3.534 3.368 -.223 -1.049 .306

(Constant)grade point average

Model1

B Std. Error

UnstandardizedCoefficients

Beta

StandardizedCoefficients

t Sig.

Dependent Variable: jail sentencea.

Sentence = -3.5 G.P.A. + 18

Page 18: Statistics & SPSS Review

Correlation

Page 19: Statistics & SPSS Review

Correlation: Sentence & G.P.A.

Correlations

1 -.223. .306

23 23-.223 1.306 .

23 24

Pearson CorrelationSig. (2-tailed)NPearson CorrelationSig. (2-tailed)N

grade point average

jail sentence

grade pointaverage jail sentence

Page 20: Statistics & SPSS Review

Correlation: Sentence & G.P.A.

Correlations

1 -.223. .306

23 23-.223 1.306 .

23 24

Pearson CorrelationSig. (2-tailed)NPearson CorrelationSig. (2-tailed)N

grade point average

jail sentence

grade pointaverage jail sentence

p value

Page 21: Statistics & SPSS Review

Interpreting r as r2

r = -.22 r2 = .05

G.P.A. “explains” 5% of variance in SENTENCE length

Correlation